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TCA9803: Need Confirmation Request of application circuit

Satheeshkumar Selvaraj
Prodigy 95 points
Part Number: TCA9803
Other Parts Discussed in Thread: PCA9517

Dear Specialists,

We are planning to use TCA9803DGKR as below topology. We need your confirmation/suggestion.  . 

1. Connected the B side of TCA9803 to the I2C master device side and same net is shared to PCA9517(A Side)Level translator device which is 1.8V.

2.A side of TCA9803 to three slave devices are connected which is 3.3V logic.

3.B side of PCA 9517 is connected to four slave devices, which is 3.3V logic

Is it okay to connect multiple slaves in the configuration.

Could you please see the below configuration block diagram.

Please provide your feedback.

Thanks,

S.Satheesh

  • +1
    TI__Genius 15345 points

    Hi Satheesh,

    This is fine, just make sure that you do not have pull ups on the B side of the TCA980x.

    Here are some general considerations for the TCA980x family:

    • The device cannot be connected B side to B side.
    • The B side of the bus cannot be connected to any devices that use passFET technology or that require pull up resistors
      • The B side of the bus drives it's own current so as long as your device does not require a pull up you should be fine.
    • The B side of the bus cannot be connected to any devices with rise time accelerators, external current sources, static voltage buffer outputs, outputs with RILC > 150 ohms.
    • The input and output leakage current from any of the devices connected to the B side cannot exceed their respective specs:
      • If the input leakage current is exceeded than the VILC spec may no longer be valid
      • If the output leakage current is exceeded than the device could incorrectly read that as a low and in the worst case the device could be stuck transmitting a low on the entire bus

    Best,

    Chris

  • +1 in reply to Chris Ayoub
    Prodigy 95 points

    Hi Chris,

    Thanks for you quick response.

    one doubt on below point.

     The B side of the bus cannot be connected to any devices with rise time accelerators, external current sources, static voltage buffer outputs, outputs with RILC > 150 ohms

    For my configuration TCA9803 B side is parallelly connected to PCA 9517 level convertor device hope it will not causes any problem?

    Thanks,

    S.Satheesh

  • +1 in reply to Satheeshkumar Selvaraj
    Guru 317250 points

    Only the B-side drivers of the PCA9517 have a voltage offset. Connecting TCA9803 B to PCA9517 A should work.

  • 0 in reply to Clemens Ladisch
    Prodigy 95 points

    Thanks for your confirmation